U.S. patent number 5,662,596 [Application Number 08/521,547] was granted by the patent office on 1997-09-02 for true bi-pivotal orthopedic and orthotic hinge with incremental motion control.
Invention is credited to David Ernest Young.
United States Patent |
5,662,596 |
Young |
September 2, 1997 |
True bi-pivotal orthopedic and orthotic hinge with incremental
motion control
Abstract
The hinge has optimally spaced pivots in which extension and
flexion travel of each independently pivoted hinge arm is limited
by a series of planar metal stops acting on both arms and in both
directions. Each stop has first and second pairs of angled stop
faces for limiting extension at optionally different angles and
first and second pairs of angled stop faces for limiting flexion at
optionally different angles. The hinge arms are disposed between a
front plate and a back plate and pivot means for each hinge arm
also serve as securing means securing the plates and hinge arms
together. Each stop is secured by a single screw which passes
through one plate. Stops are mounted in the internal flexion angle
of the hinge.
Inventors: |
Young; David Ernest
(Watlington, Oxfordshire, OX9 500, GB) |
Family
ID: |
24077166 |
Appl.
No.: |
08/521,547 |
Filed: |
August 30, 1995 |
Current U.S.
Class: |
602/26;
602/16 |
Current CPC
Class: |
A61F
5/0123 (20130101); A61F 2005/0167 (20130101) |
Current International
Class: |
A61F
5/01 (20060101); A61F 005/01 () |
Field of
Search: |
;602/16,26 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1299455 |
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Apr 1992 |
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CA |
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0 301 817 |
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Jan 1989 |
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EP |
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0 327 286 |
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Sep 1989 |
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EP |
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615734 |
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Sep 1994 |
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EP |
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88/5584 |
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Jun 1989 |
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ZA |
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2182714 |
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May 1987 |
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GB |
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2207458 |
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Feb 1989 |
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GB |
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2208065 |
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Feb 1989 |
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GB |
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Primary Examiner: Apley; Richard J.
Assistant Examiner: Risley; David R.
Attorney, Agent or Firm: Tilton Fallon Lungmus
Claims
I claim:
1. An orthopedic bi-pivotal hinge comprising a hinge body having a
pair of plates defining a space therebetween; two hinge arms having
extended adjacent end portions located in said space and
independently pivotally connected to said plates for pivotal
movement of said each arm in directions of extension and flexion
independent of the other of said arms; and a generally
diamond-shaped insert element removably secured between said plates
having a central body portion and a plurality of corners with a
pair of angularly-oriented stop faces adjacent to each corner; said
pairs of stop faces constituting abutment surfaces; each said hinge
arm being engagable with one of said surfaces for limiting the
extent of pivotal movement in extension and being engagable with
the other of said surfaces for limiting the extent of pivotal
movement in flexion said body portion being generally coplanar with
said hinge arms and extending partially therebetween; and
connecting means removably securing said body portion of said
insert element to said hinge body.
2. The hinge of claim 1 in which said body portion of said insert
element has a single opening therein; said connecting means
comprising a single screw element securable to said plates and
extending through said opening for releasably securing said insert
element within said space.
3. The hinge of claim 1 in which said abutment surfaces are each
disposed at a selected angle within the range of
0.degree.-65.degree. measured from a line passing through the two
pivot axes of said bi-pivotal hinge.
4. The hinge arm of claim 3 in which two of said abutment surfaces
are on opposite sides of an apical line perpendicular to a line
passing through both of said pivot axes and being located with said
apical line spaced equidistant from said pivot axes; said abutment
surfaces being at the same angle relative to said line passing
through said two pivot axes.
5. The hinge of claim 1 in which a second generally diamond-shaped
insert element is provided; said second insert element being
interchangeable with said first-mentioned insert element and
differing from said first-mentioned insert element essentially by a
difference in the angular orientation of each pair of said stop
thereof.
6. An orthopedic and orthotic bi-pivotal hinge comprising a body
having a front plate and a back plate disposed in parallel relation
and defining a space therebetween; two hinge arms having adjacent
end portions located in said space and independently connected to
said body along two spaced pivot axes for independent movement of
each arm in directions of and flexion; said end portion of each
hinge arm having a longitudinal extension defining a first
posterior edge portion providing an extension-limiting abutment
face; each hinge arm having a second posterior edge portion spaced
from said first posterior edge portion and defining a
flexion-limiting face; a generally diamond-shaped insert element
removably secured to said body within said space said insert
element being symmetrical about an apical axis perpendicular to a
line passing through both of said pivot axes and being located with
said apical axis spaced equidistant from said pivot axes; said
insert element providing a pair of extension-limiting stop faces on
opposite sides of said apical axis with each said stop face being
engagable with said first posterior edge portion of a hinge arm for
limiting the angle of extension of said arm; said insert element
also providing a pair of flexion-limiting faces along opposite
sides of said apical axis with each said flexion-limiting stop face
being engagable with said second posterior edge portion of a hinge
arm for limiting the angle of flexion of said arm.
7. The hinge of claim 6 in which said insert element has a single
opening therein; said connecting means comprising a screw element
securable to said side walls and extending through said opening for
releasably securing said insert element within said space.
Description
FIELD OF THE INVENTION
This invention relates to hinges employed in orthoses and
orthopedic braces used on the human body, particularly the knee
joint. In particular, the invention relates to novel means for
limiting the flexion and extension travel of the arms of a true
bi-pivotal hinge.
BACKGROUND OF THE INVENTION AND THE PRIOR ART
There are many hinge designs used in orthopedic splints and braces
employed at the knee.
In a first widely used type, there are two hinge arms joined at and
flexing about a single pivot. This type is generally referred to by
those skilled in the art as the uni-axial, uni-pivotal or
monocentric type.
In a second type, perhaps even more widely used, there are two
hinge arms each having its own pivot and also each having a set
gear teeth about the periphery of the part which extends between
the pivots. The arms are so sized and arranged that the gear teeth
mesh between the pivot points thereby integrating the arm
movements. Thus if one arm moves, the other must move as well. This
type is generally referred to by those skilled in the art as the
geared bi-axial, geared duocentric or geared polycentric type. The
latter term is perhaps the most widely recognized.
Neither of these hinge types is remotely physiological in the way
they move and because their mechanical action is so unlike that of
the human knee their use in a brace construct may be positively
deleterious to an injured, repaired or deformed knee.
The term brace construct is used by those skilled in the art to
describe the resultant mechanical arrangement of a brace and the
leg to which it is attached. A combination of casting materials
(such as Plaster of Paris or resin impregnated bandages) and cast
bracing hinges as well as braces secured on the leg by means such
as straps are brace constructs once they are in place on the
leg.
Mechanically, the knee is a modified, crossed, four bar linkage
comprising the rigid elements femur, tibia and the anterior and the
posterior cruciate ligaments. Its axis of rotation moves backwards
or posteriorly as the knee is flexed from the fully extended
position. The locus or track of the axis of knee rotation is called
the "Instant Center Pathway" which exactly defines the moving path
of the center of knee rotation at any given instant. Uni-axial and
geared polycentric hinges do not have this construction; they do
not move in this manner and within a brace construct they cannot
accommodate or track the complex motion of the knee properly.
Another type of hinge design used in orthopedic splints and braces
employed at the knee has two hinge arms each having its own pivot
but in this design there are not gear teeth. Thus, in this type,
the arm movements are not integrated and each arm can always move
independently without affecting the other. This type of hinge is
generally referred to by those skilled in the art as the true
bi-axial, true bi-pivotal or simply just bi-pivotal type. It
continues to grow in popularity with the realization that such a
construction is superior to the others in providing the freedom
necessary to accommodate the complex and changing locus of the axis
of the knee throughout the entire flexion/extension cycle.
Both bi-pivotal hinges and geared polycentric hinges are, in
mechanical terms, three bar linkages. However, the geared
integration of the hinge arms in the geared polycentric type arms
causes the loss of one degree of freedom. When used in most
orthopedic braces both types require at least one stop at or near
the fully extended position to prevent over-travel of the knee into
hyperextension. In bracing and general orthopedic and orthotic
applications a three bar linkage hinge mechanism, with all degrees
of freedom available, offers the most practical and appropriate
mechanical arrangement for accommodating the complex motion of the
knee.
The present author has been concerned for many years with research
and development of bi-pivotal hinges based upon pivot spacings
between 24 mm and 30 mm. When such hinges are used as part of a
brace construct, the net rearward travel of the instant center
pathway of the knee axis which can be accommodated approximates to
that which is likely to be encountered in the great majority of
patients. This was confirmed at Sheffield and Brunel Universities
in the United Kingdom in 1986 and 1987.
In addition it was confirmed, in 1984, by means of combined video,
computer and force-plate gait analysis, that when used at the knee,
bi-pivotal hinges with such pivot spacings introduce less
disturbance to the normal gait (or walking pattern), than either
geared polycentric two-pivot hinges or uni-axial hinges.
Furthermore, it has been shown that pistoning and zig-zagging does
not occur in such hinges (provided they are fitted properly) when
the knee is under load. This work was carried out at Derby Royal
Infirmary, Derby, United Kingdom in 1984 and was presented at the
8th World Orthopaedic Congress in Washington, DC, USA, May 4-10,
1987 by Dr. David Pratt. Dr. Pratt's principal co-author was David
Rowley, M.D., F.R.C.S., now Professor of Orthopaedics and Trauma
Surgery, The University, Dundee, Scotland.
By way of contrast, if geared polycentric hinges are restrained at
a point along each hinge arm some distance from each pivot and
flexed, they are driven forwards in the opposite direction to
natural knee motion. In a brace construct this is exactly the form
of restraint applied, usually by sets of securing straps above and
below the knee. This movement is easy to demonstrate in a brace not
in place on a leg. However, in a brace construct movement is
substantially prevented by the securing straps and the net effect
is to generate forces which act counter to the flexing forces
generated by the flexor muscle groups acting on the knee. The
opposite effect is encountered during extension of the knee in such
a brace construct and in both cases, the resolution of these
extraneous forces is through a compromised knee joint.
It is possible, by altering the architecture of a geared
polycentric hinge, to partially alleviate these effects. This can
be done, for instance, by introducing a substantial anterior
displacement of the femoral hinge arm and a substantial posterior
displacement of the tibial hinge arm and arranging the gearing
accordingly. Such an arrangement is taught in U.S. Pat. No.
4,697,583 to Mason et al., assigned to Don Joy Orthopedic Inc. of
Carlsbad, Calif., USA.
Another concern to those who have to set up and adjust braces is
the total number of parts to be handled when a brace needs
adjustment. This is a particular problem with braces which have
incremental extension and flexion stop. In every commercially
available system known to the present author which employs
incremental stops, extension stops and flexion stops are secured
separately by at least one screw for each stop and there is often a
hinge cover which has to be removed as well. This is the case with
a 1995 released product from Don Joy Inc. of Carlsbad, Calif., and
called "Legend".TM. which is admittedly a geared polycentric
device. In this product, two screws on each hinge release a hinge
cover, a flexion stop and an extension stop. To make any change, at
least two further stops must be selected and handled from a choice
of four different extension stops (8 in total) and four different
flexion stops (8 in total).
This calls for a minimum of four screws, two hinge covers and four
stops (two outgoing and two incoming)--10 parts plus the selection
of two of these from a minimum of eight--to be handled at any given
stop change. This level of handling is not particularly unusual in
prior art braces but it is very time consuming.
However, the present invention is concerned solely with art of
bi-pivotal hinges and further references to the prior art will be
so restricted. The present author has been the first inventor of a
number of adjustment mechanisms for true bi-pivotal hinges
providing continuously variable stops. These are described in
patents GB 2 182 714 and U.S. and EPO counterparts U.S. Pat. No.
4,915,098 and 327286, respectively, U.S. Pat. No. 5,000,170 and
Canadian counterpart 1 299 455; GB 2 208 065 and U.S. counterpart
U.S. Pat. No. 4,881,299 and U.S. Pat. No. 5,039,247.
A series of patents to Borig et al. is relevant to continuously
variable stops in bi-pivotal hinges and comprises UK 2 207 458 and
counterparts U.S. Pat. No. 4,881,532, EPO 301817, AUS 79761 and SA
88/5584.
In addition, the present author is first inventor of U.S. Pat. No.
5,038,765 which discloses selectable "T"-shaped inserts with
abutment stops for limiting angular travel of one movement of both
arms of a true bi-pivotal hinge. As generally disclosed, this
movement is extension, which is undoubtedly the most usual movement
which would be required to be controlled. However, claim 1 is not
limited to extension and it is clear that flexion, alone, could
also be limited as taught. In such a flexion limiting
implementation, separate means for at least preventing
hyperextension, would necessarily have to be included.
A brace embodying these inserts for limiting extension travel has
been sold for several years, by leading companies, including
recently by Johnson and Johnson Professional of Raynham, Mass., and
Bracknell, Berkshire, United Kingdom in a number of countries,
including the United Kingdom and the United States. The product is
sold under the commercial name Masterbrace.TM. and is manufactured
by Protectair Limited, Abingdon, Oxfordshire, United Kingdom.
The present author is aware of few other commercially available
examples of true bi-pivotal hinges and has found few relevant
references in the art via patent and commercial literature
searches.
In recent years a great deal of attention has been paid by those
skilled in the art to the design of functional knee braces which
are intended to provide stability for unstable knees. current
opinion favors designs in which hinges are disposed in close
approximation to the knee, have minimal thickness profiles and
generally offer limited control of extension and flexion.
Accordingly, continuously variable stop mechanisms are now mainly
found in rehabilitation braces which are used immediately following
injury or repair to knee ligaments and are otherwise generally
simpler braces. In those patients at a later stage of
rehabilitation and returning to active sport, discontinuous or
incremental stop mechanisms are acceptable in the functional knee
braces typically prescribed at that stage.
A functional knee brace known to have been made and sold by Messrs.
Omni Scientific of Martinez, Calif., is believed to be based on
Anderson, U.S. Pat. No. 4,249,524. This teaches a true bi-pivotal
hinge; however, the pivots are very widely spaced. It seems
inevitable that, in such a hinge, shortening would occur during
flexion, leading to effective shortening of a cast or brace in
which it was used. Such shortening would allow the injured or
recently repaired knee joint to piston and to experience
undesirable loads.
In the Anderson patent, the hinge center bar apparently fulfills
the function of both a mounting for the pivots and for the hinge
arms since it extends to a position where members, normally termed
headplates or limb bands, would be employed.
For instance, in a functional knee brace intended for use by a
person returning to active contact sport following a ligament
injury, there is an expectation, not always justified, that the
brace will provide physical protection for the knee. If wide
pivotal spacing is employed on the lateral hinge, the medial
collateral ligament will receive little, if any, protection from
the brace if a substantial, medially directed, lateral blow is
suffered when the knee is moderately flexed.
Although Anderson briefly mentions stops, no motion control system
is disclosed in any detail. In any such system, the
inter-relationship between the control of motion and the pivot
spacing in true bi-pivotal hinges is of paramount importance.
Directly relevant is U.S. Pat. No. 4,520,802 to Mercer and Aaserude
which teaches another bi-pivotal cast bracing hinge featuring wide
pivot spacing. These authors disclose a motion control system based
preferably upon multiple indexing blocks.
As written, the intention seems to be to provide mainly flexion
control for a true bi-pivotal hinge on at least one flex bar
(frequently termed a hinge arm by other authors). FIGS. 1 and 5
support this view since it is clear in these drawings that
extension is limited only by the fundamental provision of
hyperextension stop means represented by element 23. The
specification is confusing in that element 5 is described as a
support bar or rod but in FIGS. 1 and 4 it appears to be
illustrated as a screw or pin structure which might be means of
limiting extension but which is not described as such.
Dispositions of the indexing blocks are disclosed both beyond and
between the pivots although claim 1 is limited to the latter
position. It is certainly not possible to envisage any method or
means within the scope of this disclosure by which more than one
flex bar could be controlled by one index block if it were disposed
beyond one pivot. It is also very difficult to envisage how closely
spaced pivots could be employed if two index blocks were disposed
between the pivots.
The detailed description states, in column 6 at line 27, a
preference for a pair of index blocks, thereby contemplating the
use of a single structure. No means is actually taught for
accomplishing this and it is neither clear nor obvious from any
part of the disclosure how this might be achieved. In claim 1, the
authors refer to a structure involving a pair of index blocks and
it is clear that these are intended to be used together and
disposed between the pivots.
For instance, in FIG. 1, there is shown an arrangement of two
indexing blocks disposed between the pivots, necessitating a
minimum distance between the pivots of two indexing block widths,
plus an allowance for the ends of the flex bars sufficient to
create a flexion stop on each and leaving sufficient metal about
the pivots to ensure structural integrity and durability. In such a
case, the argument applied to wide spacing in relation to the
Anderson patent op cit applies. In FIG. 5, where two indexing
blocks are disposed outside the pivots, there is no need for the
wide spacing shown but one block could not control both pivots.
In addition, it seems clear from drawings 1 and 5b and the detailed
description, that the authors did not contemplate the provision of
both flexion stops and extension stops on one indexing block. It
also seems at least likely that the means for providing extension
was intended to be conveyed by a description of element 5, the
description of which as a "support bar or rod" duplicates the
description of element 1.
In the structure as disclosed, it would be impossible to fit a
single indexing block, even with extension stops, since the
broadest dimension of such a block would have to be introduced
through a narrower dimension between those portions of the flex
arms extending between the pivots, in order to reach and act upon
on the extension surfaces of the flex bars which come to rest
against the back of center bar element 23.
With two indexing blocks, intended to offer extension stops, the
pivot spacing would have to be widened still further to allow
introduction of both blocks and this would, in any case, be
physically difficult. Once again the general argument applied to
wide spacing would detract from the usefulness of such a hinge.
FIG. 3, in conjunction with the paragraph commencing at line 36 of
column 6 seems to indicate clearly the authors' intentions, namely
that the second class of face designated 14, abuts the back of
center bar 23 (FIG. 1) locking index block 3 in position whichever
flexion stop face is selected. If this condition is fulfilled, it
becomes geometrically impossible to incorporate flexion stop faces
and extension stop faces together within a single index block 3.
This applies regardless of whether one or two are used, in any
rational orthopedic or orthotic hinge device. The provision of
structural element 23 appears crucial to the implementation of
index blocks as taught by Mercer and Aaserude.
SUMMARY OF THE INVENTION
The present invention provides a true bi-pivotal hinge, for
orthopedic and orthotic braces used on the human body and
particularly at the knee, which has an improved incremental motion
limiting mechanism.
In the invention, a true bi-pivotal hinge is provided with a series
of novel, more or less diamond-shaped, interchangeable, metal,
combined extension and flexion insert stops. Each insert stop body
provides at least one and optionally two different angular settings
for extension limitation and at least one and optionally, two
different angular settings for flexion limitation. In this novel
arrangement it is not necessary to have any part of the insert stop
accommodated and disposed between the extreme ends of the hinge
arms between the pivots.
The arrangement of the invention allows the instant hinge to have
narrow pivot spacing in the range 24 mm to 30 mm, which is the
optimal arrangement for a true bi-pivotal hinge. This is because
the modified, crossed, four-bar linkage mechanism of the human knee
has an instant center pathway which tracks posteriorly as the knee
travels from full extension to full flexion by a similar distance.
Such an unconstrained bi-pivotal hinge, which is a three-bar
linkage, offers excellent practical accommodation, during flexion
and extension motion, of the complex motion of the knee's four-bar
linkage mechanism. This is accomplished without the introduction of
extraneous forces associated with the use of uni-axial and geared
polycentric hinges.
In this invention, there is no requirement for a structure within
or formed by the hinge body to lock the stop in place after it has
been secured in place. Each diamond-shaped insert stop is secured
by a single screw which passes through either the front plate or
back plate of the hinge. This feature, together with the optional
plurality of different extension stop angles and optional plurality
of different flexion stop angles provided on each insert stop
allows quicker, easier and more economical adjustment of angular
hinge arm travel than is achievable with prior art extension and
flexion stops mechanisms for bi-pivotal hinges.
The ease of use of the instant invention is further enhanced by the
geometric structure which allows a pair of extension stop faces not
in use to be employed as a tab or handle for introducing that pair
which is required into the hinge body. The insert stop body may
also be held in the correct position by this means whilst the
securing screw is placed and driven home.
According to the invention, there is provided a true bi-pivotal
hinge, with narrow pivot spacing, for use in orthopedic and
orthotic braces which has a series of single, flat,
interchangeable, incremental insert stops made in suitable metals
such as titanium or stainless steel and which are secured in the
flexion angle of the hinge.
According to the first aspect of the invention, the incremental
metal insert stops have a first pair of angled extension stop
faces, one for each independently pivoted hinge arm, each face
being disposed at half the total extension stop angle required.
According to the second aspect of the invention, the incremental
metal insert stops have a second pair of angled extension stop
faces, one for each independently pivoted hinge arm, each face
being disposed at half a total extension stop angle required and
optionally differing from the first extension stop angle by a
clinically useful increment.
According to a third aspect of the invention, the incremental metal
insert stops have a second pair of angled flexion stop faces, one
for each independently pivoted hinge arm, each face being disposed
at half the total flexion stop angle required.
According to a fourth aspect of the invention, the incremental
metal insert stops have a second pair of angled flexion stop faces,
one for each independently pivoted hinge arm, each face being
disposed at half a total flexion stop angle required and optionally
differing from the first extension stop angle by a clinically
useful increment.
According to a fifth aspect of the invention, each interchangeable
metal insert stop body is secured by a single screw which passes
non-threadedly through either a front plate or back plate of the
hinge body and which is received threadedly into the stop body.
According to a sixth aspect of the invention, the end portion of
each approximately diamond-shaped insert stop having the pair of
angled extension stop faces not selected may be used as a handle or
grip for introducing the selected pair of angled extension stop
faces into the hinge body at the time of fitting or removal.
According to a seventh aspect of the present invention, each insert
stop body is provided with markings which clearly indicate the
total angular values of each pair of flexion and extension
stops.
It is, therefore, the principal object of this invention to provide
a true bi-pivotal hinge for use in orthopedic and orthotic braces
having narrow pivot spacings, preferably disposed apart by a
distance measurement between centers in the range 24 mm to 30 mm
and provided with a series of interchangeable, flat, metal, more or
less diamond-shaped insert stops each offering a plurality of
paired extension stops and a plurality of paired flexion stops for
limiting extension and flexion travel of both the hinge arms.
It is another important object of this invention to provide a
series of insert stops each offering first and second pairs of
angled extension stop faces, each angled face within each pair
being intended to cooperate with one independently pivoted hinge
arm and also being disposed at half a total extension stop angle
required. Additionally, the total extension stop angle presented by
the first pair of extension stop faces optionally differs from that
presented by the second pair of extension stop faces by a
clinically useful angular increment.
Other objects and advantages will become clear as the present
invention is described in greater detail, by way of example only,
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In general, a convention of describing the position of structural
elements in drawings in relation to their anatomical disposition
has been adopted using terms such as `anterior` and `posterior` to
describe fore and rear with respect to a human body upon which the
device of the instant invention would be applied.
FIG. 1 is a lateral front view of an orthopedic knee brace fitted
with a fully assembled true bi-pivotal hinge according to the
present invention.
FIG. 2 is a lateral front view of part of an orthopedic knee brace
fitted with a true bi-pivotal hinge with the hinge cover and front
plate partly cut away to show part of a first combined extension
and flexion insert stop according to the present invention. The
hinge arms are shown extended against the stop.
FIG. 3 is a lateral front view of the instant hinge with the hinge
cover and front plate removed to show a second view of a first
combined extension and flexion insert stop with the hinge arms
flexed against the stop.
FIG. 4 is a lateral front view analogous to FIG. 3 showing a first
view of a second combined extension and flexion insert stop
according to the present invention. The hinge arms are shown
extended against the insert stop.
FIG. 5 is a lateral front view analogous to FIG. 2 but with
slightly different parts of the hinge cover and front plate cut
away and a showing a second view of part of a second combined
extension and flexion insert stop according to the present
invention. The hinge arms are shown flexed against the insert
stop.
FIGS. 6, 7 and 8 are front or lateral views of further combined
extension and flexion insert stop configurations according to the
present invention.
FIG. 9 is a posterior view of a hinge according to the present
invention with a combined extension and flexion insert stop in
place.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
With general reference to FIGS. 1-9, a true bi-pivotal hinge
according to a preferred embodiment of the present invention, has
the general designation 10 and is generally represented as part of
an orthopedic knee brace 12. It is to be understood that hinge 10
will generally but not always, be used in a paired configuration
with one such structure being disposed medially and the other
laterally with respect to the human knee. Hinge 10 comprises the
major structural elements first and second substantially flat hinge
arms 14 and 16, a substantially flat front plate 18 and a
substantially flat back plate 20. These elements are conventionally
made in metals such as aluminum or titanium. As described, hinge 10
is not a handed structure.
Front plate 18 and back plate 20 are disposed in a parallel
relationship and hinge arms 14 and 16 are disposed between them,
each being independently pivotally mounted upon pivot rivet axis
means 22 and 24 (shown in section in FIGS. 2-5) provided with
bushing means 26 and 28 (28 is shown in section in FIGS. 2-5; 26 is
shown in section in FIGS. 3 and 4). The spacing between the centers
of 22 and 24 is strongly preferred to be in the range 24 mm-30
mm.
In the embodiment illustrated, hinge arms 14 and 16 are overmolded
in a suitable soft but durable material such as an injection
molding grade of synthetic rubber indicated at 30 and 32.
Additionally, hinge 10 has a front cover 34, conveniently made in
molded plastics. The first purpose of overmolds 30 and 32 and hinge
cover 34 is to ensure that metal parts do not impinge upon the
person of the wearer and also if the device were to be used in
contact sports to protect another participant. A second purpose is
to enhance the cosmetic appearance. Hinge cover 34 has a further
purpose which will be described, in context, below.
Each of hinge arms 14 and 16 has an extension 36 and 38 which
extends beyond and between pivot rivets 22 and 24, respectively but
which neither interdigitates with nor touches the other. Posterior
edges 40 and 42 of extensions 36 and 38 and the non-overmolded
posterior edges 44 and 46 of hinge arms 14 and 16 which lie
disposed between front plate 18 and back plate 20, constitute
abutment faces. Abutment faces 40 and 44 lie in the same plane and
when hinge arm 14 is in full extension these faces are also
parallel to a line c---c.sup.1 between pivot rivet axis means 22
and 24.
Abutment faces 40, 42, 44 and 46 cooperate with corresponding
structures, described below, provided by each and every one of a
series of approximately diamond-shaped combined extension and
flexion insert stops. Five insert stops in such a series are
illustrated and are designated 100, 200, 300, 400 and 500. However,
it is to be understood that whilst some of these insert stops are
typical of those which may commonly be used, they represent only a
few of the possible combinations which may be made or required in a
rational clinical range from full extension or 0.degree. to about
130.degree. flexion.
Combined extension and flexion insert stop 100 has a structure
which is typical of the series. It is planar and made of suitable
metals, such as titanium or stainless steel and has a thickness
substantially the same as hinge arms 14 and 16. Insert stop 100 has
a stop body 102 provided with a threaded hole 104. Threaded hole
104 provides means by which insert stop 100 is secured, threadedly,
by screw 48 (shown in section in FIGS. 3-5) to and against front
plate 18 and hinge cover 34. Front plate 18 has a hole 50 (seen
only in FIG. 5) for receival, non-threadedly, of screw 48 with
minimal clearance. Hinge cover 34 has a tapered recess 52,
centrally positioned in which is a hole (not seen) also for
receival, non-threadedly, of screw 48. When screw 48 is driven
fully home, its head 54, lies just under flush with the surface 56
of hinge cover 34.
As may be seen by reference to FIGS. 3, 4 and 5, the center of hole
50 in front plate 18 is located on a line n-n.sup.1 normal to and
running posteriorly from center line c-c.sup.1. This line also
bisects the distance between the centers of pivots 22 and 24. The
position of hole 50 is selected to optimize the geometrical
solutions applied to the selection of insert stops.
As may be seen by brief reference to FIGS. 6-8, insert stops are
symmetrical about an axis a-a.sup.1 which runs from the apex of the
first total extension stop angle to the apex of the second total
stop angle. Insert stops are not necessarily symmetrical about an
axial line b-b.sup.1 drawn between the apices of angles between
adjacent flexion stop faces. However, the position of the center of
the threaded securing hole illustrated at 104, 204, 304, 404 and
504 in the drawings always lies at the intersection of lines
a-a.sup.1 and b-b.sup.1.
Insert stop geometry will be strongly influenced by the required
stop angles selection but other factors, such as the width of hinge
arms 14 and 16, the shape and position of extensions 36 and 28 and
the overall shape and size of hinge body 10 and its other major
components, are important.
For clarity lines a-a.sup.1 and b-b.sup.1 will be referred to in
the general text, hereinafter, as "vertical apical axis" and
"horizontal axis", respectively.
In insert stop 100 each member 106, 108 of a first pair of
extension stop faces is symmetrically disposed either side of a
vertical apical axis at an angle of 5.degree. to and above a
horizontal axis, thus presenting, as illustrated in FIG. 2, a total
extension stop angle of 10.degree. to abutment faces 40 and 42 of
extensions 36 and 38 of hinge arms 14 and 16, respectively. Each
member 110, 112 of a second pair of extension stop faces is also
symmetrically disposed either side of the vertical apical axis at
an angle of 10.degree. to and below the horizontal axis, thus
providing, when required, a second total extension stop angle of
20.degree. for abutment faces 40 and 42.
As best seen in FIG. 1 at enlarged scale, that part 114 of stop
body 102 which is adjacent to stop faces 110, 112 also functions as
a tab or handle. This feature is useful when changing entire insert
stops or switching stop values. For instance, in order to use the
second pair of extension stop faces 110, 112 and provide hinge 10
with 20.degree. of extension block, screw 48 is removed and stop
100 is readily withdrawn using handle 114. Insert stop 100 is then
reversed and handle 116, which is the equivalent part of stop body
102 adjacent to stop faces 106, 108 (seen in FIGS. 2 and 3) is used
to introduce extension stop faces 110, 112 into the correct
position within hinge 10. Handle 116 may also be used to hold
insert stop 100 in position while screw 48 is relocated and driven
home. Provided hinge arms 14 and 16 are extended and flexed against
insert stop 100 before screw 48 is fully tightened, stop 100 will
center itself and line up properly without the need for secondary
adjustment of its position.
In insert stop 100 each member 118, 120 of a first pair of flexion
stop faces is symmetrically disposed either side of the vertical
apical axis at an angle of 65.degree. to and above the horizontal
axis. This arrangement presents, as illustrated in FIG. 3, a total
flexion stop angle of 130.degree. to abutment faces 44 and 46. Each
member 122, 124 of a second pair of flexion stop faces is also
symmetrically disposed either side of the vertical apical axis at
an angle of 65.degree. to and below the horizontal axis thus also
providing a total flexion stop angle of 130.degree. for abutment
faces 44 and 46.
Radii 126, 128, 130 and 132 all have the same dimension, which is
somewhat greater than the radium of curved portions 58 and 60 of
hinge arms 14 and 16. This arrangement is to ensure clearance
between insert stop 100 and hinge arms 14 and 16 at all positions
of hinge arm travel between selected extension stop faces and
selected flexion stop faces. These radii are all tangential to a
circle centered upon the intersection of axes a-a.sup.1 and
b-b.sup.1. This confers the basic diamond-shape upon the central
body portion of all insert stops. The radii add concavity to the
sides and the stop selection superimposed upon this basic
architecture dictates the final shape which varies considerably
within the overall basic diamond pattern.
Thus, single combined extension and flexion insert stop 100,
located in the net flexion angle of hinge 10 offers extension
blocking at 10.degree. and 20.degree. each with, effectively full
flexion. This is a rational and desirable set of combinations for a
knee in the later stages of rehabilitation following surgical
repair to a ruptured anterior cruciate ligament (ACL). A healthy
knee, without a brace fitted, may well flex beyond 130.degree. but
with a brace in place, above and below knee structures thereof will
generally impinge upon one another at large flexion angles. In any
case, insert stops according to the present invention may readily
be made with any required flexion angle value.
Combined extension and flexion insert stop 200 is analogous to
insert stop 100 and has the equivalent structures 202-232. If
differs only in that extension stop faces 206, 208 are
symmetrically disposed either side of the vertical apical axis at
an angle of 15.degree. to and above the horizontal axis and
presents, as illustrated in FIGS. 4 and 5, a total extension stop
angle of 30.degree. to abutment faces 40 and 42. Also, extension
stop faces 210, 212 are symmetrically disposed either side of the
vertical apical axis at an angle of 20.degree. to and below the
horizontal axis providing, when required, a second total extension
stop angle of 40.degree. for abutment faces 40 and 42. Both total
flexion stop angles are 130.degree., as in insert stop 100.
Combined extension and flexion insert stops 300, 400 and 500, shown
isolated in FIGS. 6-8, are also analogous to insert stop 100 and
have the equivalent structures 302-332, 402-432 and 502-532. These
insert stops are included to allow a discussion of the rationale
for stop selection and of apparent limits of the diamond pattern
architecture related to materials selection.
In FIG. 6, insert stop 300 has first and second pairs of extension
stop faces 306, 308, 310, 312. Both pairs provide an extension stop
angle of 0.degree., which is full extension. Insert stop 300 also
has first and second pairs of flexion stop faces 318, 320; 322, 324
both of which offer a flexion stop angle of 45.degree. for abutment
faces 44 and 46.
Insert stop 300 is not truly rational under the present invention,
an important advantage of which is to provide multiple combinations
of extension and when required, flexion as well. It is included
because it represents a worst-case scenario for the instant insert
stops when under load. As seen in FIG. 6, insert stop 300 has
narrow left and right extremities in the region of flexion stop
faces 318, 320 and 322, 324, respectively. A 45.degree. flexion
stop setting is a most unlikely selection in a modern functional
bracing based treated regime for late rehabilitation following ACL
or other ligamentous reconstruction and is outside the present
author's experience. Furthermore, as discussed in the preamble,
braces used earlier in the post-operative phase are usually
preferred with continuous control of flexion and extension.
Nonetheless, it is not wished to limit the invention and it is for
this reason that the insert stops are recommended to be made in the
preferred metals. With such metals used in thicknesses likely to be
preferred for hinge arm construction, tests have shown that insert
stops configured as in 300 are adequate to withstand forces likely
to be encountered during use.
In FIG. 7, insert stop 400 represents a more rational but still
rather unusual combination in which the first pair of extension
stop faces 406, 408 present a total extension stop angle of
10.degree. and the second pair of extension stop faces 410, 412
present a total extension stop angle of 20.degree.. Both pairs of
flexion stop faces 418, 420; 422, 424 present a total flexion stop
angle of 60.degree.. This insert stop is mainly included to
indicate, by comparison with FIG. 6, that the amount of stop
material available to support compression loads in flexion
increases rapidly with increasing flexion stop angle. Insert stop
400 in FIG. 7 is shown with suitable preferred markings. The
convention of marking each portion of a stop with the setting it
actually has rather than those of the opposite end, is preferred as
less confusing.
In FIG. 8, insert stop 500 represents a rational combination in
which the first pair of extension stop faces 506, 508 present a
total extension stop angle of 10.degree. and the second pair of
extension stop faces 510, 512 present a total extension stop angle
of 20.degree.. Both pairs of flexion stop faces 518, 520; 522, 524
present a total flexion stop angle of 90.degree.. This insert stop
is also included partly to indicate further, by comparison with
FIGS. 6 and 7, that the amount of stop material available to
support compression loads in flexion increases rapidly with
increasing flexion stop angle. FIG. 8 shows both pairs of extension
stop face angles and one pair of flexion stop face angles of stop
500 labeled.
In all the examples illustrated, with the exception of insert stop
300 in FIG. 6, combination stops have two extension blocking angles
and one flexion blocking angle. This reflects the fact that in
practice during later stages of rehabilitation of the knee, there
is a greater and more frequent requirement to revise extension
blocking rather flexion blocking. Those charged with the care of
patients, therefore, will often prefer to have to make less
decisions about flexion (which they will in any case choose to set
at full flexion) and have several combinations of extension stop
immediately available which involve minimal stop changes.
An advantage of the present invention is that in such a scenario,
which is very likely, a carer would need only two insert stops for
each hinge. Each insert stop would have both sets of flexion stops
providing 130.degree. of flexion block. One insert stop would offer
extension blocking at 10.degree. and 20.degree.--as illustrated
with respect to stop 100 in FIGS. 2 and 3. The other insert stop
would offer extension blocking at 30.degree. and 40.degree.. Such
an approach reduces handling of insert stops and associated parts
and thereby saves time.
Obviously a responsible manufacturer would include with a brace
incorporating a hinge or hinges according to the present invention,
a sufficient range of insert stops to cover all common clinical
circumstances and make others available as required. In fact such a
basic range, covering most needs would probably be configured as
follows:
______________________________________ Extension Extension Flexion
Flexion First Pair Second Pair First Pair Second Pair
______________________________________ Stop 1 0.degree. 0.degree.
130.degree. 90.degree. Stop 2 10.degree. 20.degree. 130.degree.
130.degree. Stop 3 30.degree. 40.degree. 130.degree. 130.degree.
Stop 4 10.degree. 20.degree. 60.degree. 90.degree.
______________________________________
Expressed differently, an orthopedic brace according to the present
invention and provided with such a set of insert stops would allow
adjustment to:
______________________________________ Full extension with
90.degree. or 130.degree. of flexion 10.degree. extension block
with 60.degree. or 130.degree. of flexion 20.degree. extension
block with 90.degree. or 130.degree. of flexion 30.degree.
extension block with 130.degree. of flexion 40.degree. extension
block with 130.degree. of flexion
______________________________________
This range, providing 8 combinations from insert 4 stop entities,
would cover most if not all requirements from early middle to late
rehabilitation in a functional knee brace, even where a surgeon
favors a "straight-through" approach. This involves using a
functional knee brace throughout treatment, eschewing the use of a
traditional so-called rehabilitation brace during the
post-operative period and thereby reducing costs.
In contrast, the incremental stop system disclosed by the present
author in U.S. Pat. No. 5,038,765 and applied in the commercial
product Masterbrace.TM., described earlier, uses four insert stops
to achieve four variations of extension block with only full
flexion being allowed. Worse cases are cited in the prior art.
In the present invention, hinge cover 34 is secured from behind
hinge 10 by a self-tapping screw 62 (shown in section in FIGS. 2
and 5). Self-tapping screw 62 passes non-threadedly through a
clearance hole 64 in back plate 20 and engages self-threadingly
with a blind pilot hole 66 in a boss 68 (both shown in hidden
detail in FIG. 1). This feature makes it unnecessary to remove or
in any other way handle hinge cover 34 during an incremental insert
stop change. In addition, since only a single screw 48 secures the
combination extension and flexion insert stops of the present
invention, the maximum number of parts which need to be handled is
much less than in prior art systems. For instance, a typical insert
stop change on a two-sided functional knee brace where extension
block is altered will involve handling only two screws and two
insert stops--four parts in all. There is a good chance no new
insert stop entities will be needed; however, even if they are
needed, the total number of parts to be handled still only rises to
six--40% less handling than that required in the 1995 geared
polycentric hinge product cited in the prior art statement.
Finally, the provision of combination extension and flexion insert
stops which feature the advantage of handles deserves some further
discussion.
In general, prior art incremental insert stops are difficult to
introduce, remove and secure and this adds to handling time and
slower patient throughout. The stop handles provided by the present
invention and exemplified by 114 and 116 in insert stop 100
overcome this problem. It might be argued that their protrusion
beyond the posterior edge of the hinge body is disadvantageous.
However, those skilled in the art will recognize that a protrusion
which is maximally about 6 mm by an unselected 40.degree. extension
stop (the maximum likely to be encountered) into the posterior,
flexion angle of the hinge, is most unlikely to be troublesome.
Any such insert stop is likely to have a 30.degree. flexion stop as
its selected functional partner. No patient wearing a functional or
other orthopedic knee brace so configured, would or could
participate in contact sports.
In contrast, insert stops according to the present invention, with
full extension provided by both first and second pairs of extension
stop faces, are likely to be used by those who participate in
contact sports. However, these insert stops will protrude only
about 3 mm into the posterior, flexion angle of the hinge which is
an insignificant hazard. Brief reference to FIG. 1, which is at
enlarged scale, will indicate how little insert stop 100 protrudes,
even with the 10.degree. extension block engaged and the 20.degree.
extension block functioning as a handle.
In a second embodiment (not illustrated) all the crucial structures
of the first embodiment are identical except that there is no hole
48 in hinge cover 34. Instead, insert stops are secured by an
identical screw passing non-threadedly through a non-threaded hole
in back plate 20 which corresponds to hole 50 in front plate 18 of
the first and preferred embodiment. This screw is received into a
tapered recessed hole in an inner hinge cover which corresponds to
52 of hinge cover 34 of the first and preferred embodiment. Such an
embodiment might be preferred if it were felt that patients would
interfere with the insert stop retaining screw. However, such a
screw citing would be impossible to access with the brace on the
patient and this would detract from some of the advantages of the
invention relating to time saving.
Whilst the present invention has been described in respect of
particular embodiments, modifications may readily be made by those
skilled in the art. It is intended that the claims should cover any
such modifications falling within the spirit and scope of the
invention.
* * * * *